fix: NsTeSTPacket.LeadingBlank defaults to empty string (20.0.1) (#459)

The field models the literal double space vanosilla emits after the
`NsTeST` header; without a non-null default the serializer emits "-"
for an unset property, producing "NsTeST - 0 …" on the wire. Make the
property non-nullable with an empty-string default so consumers don't
have to remember to set it.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: erwan-joly

src/NosCore.Packets/NosCore.Packets.csproj

@@ -12,7 +12,7 @@
 		<RepositoryUrl>https://github.com/NosCoreIO/NosCore.Packets.git</RepositoryUrl>
 		<PackageIconUrl></PackageIconUrl>
 		<PackageTags>nostale, noscore, chickenapi, nostale private server source, nostale emulator</PackageTags>
-		<Version>20.0.0</Version>
+		<Version>20.0.1</Version>
 		<PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
 		<Description>NosCore's Packets (Nostale packets) defined over classes</Description>
 		<PackageLicenseExpression>MIT</PackageLicenseExpression>

src/NosCore.Packets/ServerPackets/Login/NsTeSTPacket.cs

@@ -16,7 +16,7 @@ namespace NosCore.Packets.ServerPackets.Login
     public class NsTestPacket : PacketBase
     {
         [PacketIndex(0)]
-        public string? LeadingBlank { get; set; }
+        public string LeadingBlank { get; set; } = string.Empty;
 
         [PacketIndex(1)]
         public RegionType RegionType { get; set; }